Ultra-Violet Mie Lidar Observations of Particulates Vertical Profiles in Macao during a Record High Pollution Episode

Vertical profiles of particulates were measured in Macao by using a 355 nm Mie scattering lidar during a dust event. A high energy pulse laser was employed as the light source to detect the extinction coefficient in the atmosphere. The extinction profiles showed layers of high aerosol concentrations in good agreement with both back trajectory analysis and ground-based pollution measurements in Macao, which indicate that this lidar is very useful for monitoring extinction profiles during extreme high aerosol loading and low visibility atmospheric conditions when most low energy lidar system is inefficient. The results evidenced that correlations between PM2.5 and TSP varied with the intensity of dust storm and the PM2.5/PM10 ratio was small during dust episode, which indicated that aerosols were dominated by large particles. Furthermore, results of the dust event showed high aerosol concentrations at altitudes where the wind carried the dusty aerosols from northern China, covering Shanghai and the Taiwan Channel, to the Pearl River Delta Region. This research improved the understanding of the dust properties in Macao.

Characteristics of Volatile Organic Compounds in the Pearl River Delta Region, China: Chemical Reactivity, Source, and Emission Regions

Volatile organic compounds (VOCs) are important precursors of photochemical ozone and secondary organic aerosol (SOA). Here, hourly variations of ambient VOCs were monitored with an online system at an urban site (Panyu, PY) in the Pearl River Delta region during August–September of 2020 in order to identify reactive VOC species and major sources of VOCs, OH loss rate (LOH), SOA formation potential (SOAFP), and corresponding emission source regions. The average concentration of VOCs at PY was 31.80 ± 20.82 ppbv during the campaign. The C2–C5 alkanes, aromatics, and ≥C6 alkanes contributed for the majority of VOC, alkenes and aromatics showed the highest contribution to LOH and SOAFP. Further, m/p-xylene, propene, and toluene were found to be the top three most reactive anthropogenic VOC species, with respective contributions of 11.6%, 6.1%, and 5.8% to total LOH. Toluene, m/p-xylene, and o-xylene constituted a large fraction of calculated SOAFP. Seven major sources were identified by using positive matrix factorization model. Vehicle exhaust made the most significant contribution to VOCs, followed by liquefied petroleum gas and combustion sources. However, industrial-related sources (including industrial solvent use and industrial process emission) had the largest contribution to LOH and SOAFP. By combining source contribution with wind direction and wind speed, the regions of different sources were further identified. Based on high-resolution observation data during ozone pollution, this study clearly exhibits key reactive VOC species and the major emission regions of different VOC sources, and thus benefits the accurate emission control of VOCs in the near future.

Calculation and application of eddy dissipation rate map based on spectrum width data of a S-band radar in Hong Kong

The spectrum width data of an S-band radar in Hong Kong are used to calculate the map of eddy dissipation rate (EDR) with the objective of providing turbulence alerting service for the en-route aircraft in the Pearl River Delta region. The calculation methodology is different from that reported in the existing literature by also removing the wind shear contribution in determining the radar-based EDR. The performance of the EDR maps obtained from the conical scans of the radar is illustrated in two examples of moderate to severe turbulence reported by the aircraft. In both cases, based on the EDR values and windshear hazard factors determined from the aircraft data, the airflow disturbances could adversely affect the operation of the aircraft. By overlaying the flight route on the radar’s reflectivity imageries, it appears that, in both cases, the disturbed airflow is associated with rather intense rain cells, though they are rather small and isolated. The EDR values calculated from the radar’s spectrum width data at the locations of the rain cells are generally consistent with those determined using the aircraft’s wind measurements. From the selected cases, it seems that the radar-based EDR values have generally satisfactory quality. If such data could be available at the cockpit through data uplinking, they could be useful hints for the pilots not to fly through the rain cells but rather going around them. The methodology may be applied to the radars in the Pearl River Delta region in order to construct a three-dimensional mosaic of turbulence intensity for the assurance of aviation safety.

Effects of Haze Experiments by Artificial Intervention on Atmospheric Mixing Layer Height (MLH) and Air Pollution in Pearl River Delta Region

In this paper, the effects of 16 times of aircraft artificial intervention operations on atmospheric MLH and air pollution in Pearl River Delta Region were investigated. By analyzing the surface observation meteorological data collected hourly each day from 2015 to 2019 using the Nozaki Method and Statistical Analysis Method, the differences of MLH’s daily variations on haze and non-haze days were studied. Then the variations of MLH, pollutant concentrations and visibility before and after artificial intervention were studied. And the variations in the concentration of fine particles were obtained by analyzing the depolarization ratio’s vertical distribution detected by Guangzhou Polarized Micropulse Lidar System. Finally, the analysis of daily average air pollutant concentrations and thickness of atmospheric mixing layer, together with the analysis of MLH, surface ventilation and the corresponding pollutant concentration sequence 18 hours post-experiment can lead to effects of MLH on air pollution. The results showed that (1) MLH varies daily significantly; (2) The atmospheric MLH, air pollutant concentration and visibility vary significantly after aircraft artificial precipitation intervention: (a) the MLH and surface ventilation increase during the first three hours of rainfall; (b) the visibility increases significantly; (c) the concentrations of PM2.5 and PM10 decrease while the concentrations of coarse and modal particles show a significant trend of decrease; (d) the subsequent dilution effect on PM2.5 and PM10 also show out in a clear way, especially on PM10. The daily average concentrations of PM2.5 and PM10 are positively correlated with the daily average MLH in the region and the correlation coefficients are -0.71 and -0.63 respectively. After haze experiments by artificial intervention, PM2.5, PM10, SO2, NO2, CO and AQI indexes were negatively correlated with MLH and surface ventilation while positively correlated with O3. The research results show its value in the aspects of the atmospheric environmental quality assessment and pollutant diffusion capacity improvement in the region. It also helps in future data demonstration tests for the effects of haze experiments by artificial intervention on atmospheric turbulence and air pollution elimination. And it provides scientific decision-making basis for future relevant measures for the quality of urban atmospheric environment improvement.

Comparison of several blood lipid-related indexes in the screening of non-alcoholic fatty liver disease in women: a cross-sectional study in the Pearl River Delta region of southern China

Background Lipid metabolism disorders play a critical role in the progression of non-alcoholic fatty liver disease (NAFLD). However, the number of studies on the relationships among blood lipid-related indexes and NAFLD is limited, and few studies have emphasized the comparison of blood lipid-related indexes in the same population to identify the optimal index for NAFLD screening. This study aimed to investigate the relationships among several blood lipid-related indexes and NAFLD, and to find the index with the best screening value for NAFLD. Methods Based on a general health examination at community health service agencies in the Pearl River Delta region of China in 2015, 3239 women were recruited in this cross-sectional study. The relationships among blood lipid-related indexes and NAFLD were assessed separately by constructing multivariate logistic regression models. Receiver operating characteristic analysis was used to evaluate and compare the screening abilities of the indexes for NAFLD. All data analyses were conducted in SPSS and MedCalc software. Results Whether in the crude model or each model adjusted for possible confounding factors, the risk of NAFLD significantly rose with increasing cardiometabolic index (CMI), triglyceride glucose index (TyG), triglycerides (TG) to high-density lipoprotein cholesterol (HDL-C) ratio (TG/HDL-C), total cholesterol (TC) to HDL-C ratio (TC/HDL-C) and low-density lipoprotein (LDL-C) to HDL-C ratio (LDL-C/HDL-C). Moreover, the area under the curve (AUC) of CMI was 0.744, which was better than that of TyG (0.725), TG/HDL-C (0.715), TC/HDL-C (0.650), and LDL-C/HDL-C (0.644) (P < 0.001). In addition, the optimal cut-off points were 0.62 for CMI, 8.55 for TyG, 1.15 for TG/HDL-C, 4.17 for TC/HDL-C, and 2.22 for LDL-C/HDL-C. Conclusions CMI is easy to obtain, is a recommended index in the screening of NAFLD in women and may be useful for detecting populations that are at high risk of NAFLD.